Oldest Horned Dinosaur in North America Was the Size of a Crow

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Paleontologists originally uncovered the skull of the horned
dinosaur in 1997 — an exciting find, given that until then,
scientists had only found a handful of teeth, bones and a tail of
early horned North American dinosaurs known as neoceratopsians.
The new species, called Aquilops americanus, lived
during
the Early Cretaceous, about 107 million years ago.

"It's the first complete specimen of a horned dinosaur found in
North America from that time," said the study's lead researcher,
Andrew Farke, a paleontologist at the Raymond M. Alf Museum of
Paleontology in Claremont, California. "And it's even more
exciting because it's not at all closely related to later horned
dinosaurs from North America." [ See
photos of the horned dinosaur fossil ]

Instead, Aquilops, which means "eagle face" in Latin, is
most closely related to animals from Asia, including the
dinosaurs Archaeoceratops oshimai and Leptoceratops
gracilis.

"In most features, it's virtually identical to them," Farke told
Live Science. "And that's cool because it adds support for this
idea that, around 110 million years ago or so, there was a big
influx of animals from Asia into North America."

At that time, the distance between North America and Asia was
slightly farther than it is today, but a land bridge may have
connected the two,
allowing horned dinosaurs to walk across, said Lindsay Zanno,
an assistant research professor of paleontology at North
Carolina State University who was not involved in the study.

The tiny skull, measuring just 3.3 inches (8.4 centimeters) long,
doesn't have horns like its distant relative, the Triceratops ,
but has other features unique to horned dinosaurs. For instance,
it sports a special toothless beak, called a rostral bone, also
seen in turtles and Triceratops.

"It was probably like what you see on birds today," Farke said.
"You have a really sharp beak for cropping off vegetation," such
as ferns and flowering plants. "If you want to pick and choose
what you want to eat, it can be really nice to have a beak that
helps bite off those plants."

The rostral bone also has a little bump, which may be the
beginning of the type of horn seen in its later relatives, Farke
said.

Moreover, the dinosaur had a long, sharply pointed cavity over
its cheek region, and cheek spikes. The spikes may have served as
ornamentation or as defense, possibly as "a way to inflict pain
on a rival, if another animal got too close," Farke said.

A dental examination showed that the dinosaur had about a dozen
flat, bladelike teeth that likely sheared off vegetation, as well
as peglike teeth that could chomp up plants.

The finding will help paleontologists reconstruct the early
evolution of horned dinosaurs, Zanno said.

"Dr. Farke and his team have actually managed to go ahead and
name what is essentially the earliest definitive horned dinosaur
that we have here on the continent," she said.

The next known
horned dinosaur in North America didn't live until about 20
million years after Aquilops, and Triceratops
lived about 40 million years later, the researchers said.

Now, when paleontologists study horned dinosaurs, they "can say
some definitive things about where things like
Triceratops and its ancestors came from," said Michael
Ryan, a horned-dinosaur expert at the Cleveland Museum of Natural
History who was not involved in the study.